The technology in vortex shedding type flow meters has been making a remarkable progress in recent years. As a matter of fact, the vortex shedding flow meter is emerging as one of the most rugged and reliable flow measurement devices providing flow data with remarkably good accuracy. The vortex shedding flow meters commercially available at the present time have two fundamental weaknesses, which are, firstly, those existing vortex shedding meters lack the sensitivity required to measure flows of gaseous media at low velocities and, secondly, they are highly susceptible to noises created by the mechanical vibrations of pipe assemblies, acoustical noises transmitted through the ambient surroundings, etc. There are vortex shedding flow meters utilizing ultrasonic waves to detect the vortex shedding frequencies, which method is supposed to eliminate the problem of interference by the mechanical vibrations. However, the ultrasonic means for detecting the vortex shedding frequencies introduce other problems and limitations of far more serious nature compared with the mechanical noise problem, which includes the error introduced by the bubbles and particles suspended in the fluid medium, serious compromise on ruggedness and durability, temperature and/or pressure limitations in the application, etc.
The primary object of the present invention is to provide a vortex shedding flow meter capable of measuring flow velocities in very wide ranges from very low velocities to very high velocities.
Another object is to provide a vortex shedding flow meter of high sensitivity and high accuracy.
A further object is to provide a vortex shedding flow meter having a high degree of noise suppressing capability.
Yet another object is to provide a vortex shedding flow meter of highly rugged and durable construction, and dependable and consistent performance.
Yet a further object is to provide a vortex shedder flow meter having a wide range of applications including extreme temperatures and/or extreme pressures.
Still another object is to provide a bidirectional vortex shedding flow meter that measures flow velocities in both directions.
Still a further object is to provide a bidirectional vortex shedder flow meter including a vortex generating member of stiff elongated structure having a blunt cross section and a pair of vortex sensing members of slender elongated geometry with substantially flat cross section disposed parallel to the vortex sensing member at an upstream and a downstream position thereof, respectively.
Additionally another object is to provide a bidirectional vortex shedder flow meter including a noise canceling feature wherein the noise signals sensed by the two vortex sensing members respectively disposed at an upstream and a downstream of the vortex generating member cancel each other while the vortex shedding signals sensed by the downstream vortex sensing member provides data on flow velocities.
Additionally a further object is to provide a bidirectional vortex shedding flow meter including a pair of vortex sensing members with substantially flat midsection extending to stocky extremity experiencing an abrupt change in cross section; whereby a small amount of the lateral deflection of the substantially flat midsection of the vortex sensing member created by the vortices produces a high stress concentration at the junction of discontinuous transition in the cross section.
It is also the object of the present invention to provide a vortex shedding flow meter including transducer means installed adjacent to the junction of discontinuous transition in the cross section, wherein the transducer means converts the mechanical signal of vortex shedding to electrical signal.
These and other objects of the present invention will become clear as the description thereof proceeds.